Telephone trunking and supervisory system



E. A. MELLINGER.

TELEPHONE TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED JUNE 10, 1909. RENEWED MAY 10.1920.

Patented Jan. 25, 1921.

5 SHEETS-SHEET 1- I l IR E. A. MELLINGER.

' TELEPHONE TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED JUNE 10. 1909. RENEWED MAY 10. 1920. 1,366,539.

L 2. 9 1T ,E 5 24 is T w J 8 d5 e m W a P Wei/AH? E. A. MELLINGER. TELEPHONE TRUNKING AND SUPERVIISORY SYSTEM. APPLICATION FILED JUNE 10, 1909. RENEWED MAY 10,1920.

Patented Jan. 25, 1921.

5 SHEETS-SHEET 3- Ufa E. A. MELLINGER.

TELEPHONE TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED JUNE 10. 1909. RENEWED MAY 10,1920. 1,366,539.

Patented Jan. 25, 1921.

5 SHEETSSHEET 4.

E. A. MELLINGER.

TELEPHONE TRUNKING AND SUPERVISORY SYSTEM. APPLICATION =FlLED JUNE 10, 1909. RENEWED MAY 10,1920.

Patented Jan. 25, 1921.

5 SHEETS-SHEET 5.

wq Wwk k5 QQ @A m ig EDWARD MELLINCER, OI CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC'ELECTBIC COMPANY, OF CHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE TRUNKING AND SUPERVISORY SYSTEM.

1 Specification of Letters Patent. P t t Jan 25 1921 Application filed June 10, 909, Serial no. 50 ,261- Renewed May 10, 1920. Serial No. 350,402.

T 0 all whom it may concern:

Be it known that I, EDWARD A. MEL- LINGER, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certaln new and useful Improvement in Telephone Trunking and Supervisory Systems, of which the following is a specification.

My invention relates to telephone systems in general, but more particularly to systems in which means are provided for automat1- cally trunking or otherwise connecting between calling and called subscribers, and especially to systems in which some portion of the connection is established by a manual switchboard operator.

In systems of this kind, sometimes referred to as semi-automatic systems, I have found that it is often desirable to enable a calling subscriber to obtain connection with a manual switchboard, and to provide means whereby the operator at such switchboard may then complete the connection to the' called subscribers line, as, for example, by using the ordinary selectors and connectors for extending a trunking connection from the manual board to the line of the called subscriber. This I have found occurs, for example, where it is desired to give service between the subscribers of a manual exchange and the subscribers of an automatic exchange, as in such case it is desirable that the manual subscriber shall be able to call the operator at the manual switchboard in any suitable manner, and that the said operator shall have means for then transmit: ting electrical impulses' in the direction of the called subscriber, whereby the automatic switches are 0 erated to complete the con- 'iection from t e manual board to the line of the called subscriber. Also, in such cases it is desirable that provision be made for enabling the automatic subscribers to call the operator at the switchboard of the manual exchange, and that the equipment of the said operator be such that the connection may then be extended to the line of the called manual subscriber. I also find that for service of this kind it is desirable that the operator shall have suitable means for fully supervisin any and all connections which-are estab ished through the medium of the manual board. This is particularly desirable when the call is from a manual line to an automatic line, in which catin the tending to increase the case the operator at the manual board should be able to know when connection is establ1shed with the called line, and when the called subscriber answers.

Ob ects of my invention are, therefore, the provision of improved means for enabling a manual board operator to more efiiclently supervise connections between manual and automatic subscribers lines,- the provision of means whereby a manual board operator may connect a callin ual subscriber with a called automatic subscriber, and may th en receive signals indiwhen the called automatic line is foun and when the called subscriber answers; the provision of an improved arrangement whereby a manual board operator may supervise ual and automatic subscribers, the supervislon being over the two sides of the talking circuit; the provision of a trunk line having means for maintaining the release relay of selector energized during conversation, whereby said relay, when the talking circuit is opened at the substation, may deenergize and thereby close a trunk-release circuit extending back through the line switch of the calling subscriber, said trunk terminating in a jack at the manual switchboard; the provision of means whereby a subscribers line switch may seize a two-conductor trunk line, and whereby said line switch may be released at the proper time, notwithstandlng that said trunk line is without the usual third conductor over'which the release of the line switch is ordinarily accomplished; and the provision of certain details and features of improvement and combinations general efiiciency of a telephone exchange system of this particu-' lar' character.

To the foregoing and other useful ends manconnections between man- I my invention consists in matters hereinafter I set forth and claimed.

In the accompanying drawings there is 7 represented the central-office equipment of a of the other exchange,

switch C, there being a master switch D for controlling the plunger of the group of llne switches of which C 1s a member, and a connector switch H is allotted to the group of subscribers lines of which the line of station A is a member; and in Fig. 2 there is represented a manual exchange equipment comprising incoming and outgoing trunk lines and an operators .cord 0; and in Fig. 3 there is shown an automatic substation A the l ne conductors of which terminate in the hue switch C, the master switch D controlling the plungers of the line switches C, and there beinga first selector SWItCh and in Fig. 4 the first selector switch E 1s allotted to a trunk line terminating in the manual exchange, the first selector being shown in an operated position and 1n connection with the second selector F; and in Fi 5 there is a connector switch H, a line switch C allotted to the line of substation A and I and J represent diagrammatically central office signaling devices, the first for supplying ringing current and the second for supplying busy signal current.

As thus shown there are several batterles having their positive terminals preferably grounded. There may, however, be but one battery, or each exchange oilice may be provided with its individual battery.

The automatic substations may be of any suitable or approved type. As shown, it w1ll be seen that substation A (Fig. 3) 1s some what difierent from the usual automatic substation, being arranged and modified to operate in connection with a two-wire system that is, in a system in which'no ground connection is used at the subscribers substation.

Substation A, for example, comprises the usual receiver 2, switch hook 3, induction coil 4 which consists of the primary winding 5 and secondary winding 6, transmitter 7, condenser 8, ringer 9 and impulse wheel 10 which has the usual impulse teeth 11. The impulse wheel 10 is secured to the shaft 12 to which there is also secured the dial .(not shown). When the dial is pulled down the springs 14 and 15 are not operated; but when it returns the impulse teeth 11 are adapted to engage the cam 13 upon the end of the spring 14, and thereby carry the latter out of engagement with the spring 15. Upon the switch hook 3 there is the cam 16 which, when the switch hook is up, permits the springs 17 and 18 to engage, thereby bridging across the subscribers line conductors l9 and 20 the primary circuit including the transmitter 7 in series with the primary winding 5; but when the switch hook is lowered the spring 17 is carried out of engagement with the spring 18 and into engagement with .the spring 18, whereby the ringer 9 in series .with the condenser 8 is bridged across the line conductors 19 and 20 instead. The manual substation A (Fig. 1) is of the usual standard common battery type, with the line conductors terminating in a line switch C, which latter is like the line switch C of the line of substation A.

The operators cord circuit 0 (Fig. 2) is provided with means whereby the operator may connect a manual substation with an automatic substation of the main exchange, and whereby the operator may also connect an automatic substation of the main exchange with a subscribers station of the manual exchange. For this purpose the cord is provided with an operators set comprising an automatic calling device. The cord circuit 0 also comprises the usual supervisory relays 21, 22 and 22, supervisory lamps 23 and 24 and supervisory and listening key K.

The line switches C, C and C and master switches D and D are of the eneral type disclosed in English Patent 0. 26,301 of 1906, the Western Electrician of Chicago,

111., of January 25, 1908, and the American Telephone Journal of New York, N. Y., of June 6, 1908. The circuit connections are, however, modified to adapt the switches to operate in connection with a two-wire system-that is, a system in which there is no ground at the subscribers station.

The first selector switches E (Fig. 3) and E (Fig. 4) are of the general type shown in United States Letters Patent No. 815,321, issued March 13, 1906, to Keith, Erickson & Erickson. As shown, the bridge-cut-ofl relay and the normal conductors have been omitted, and the circuits otherwise changed, to operate conjointly with the line switch C. The second selector F is very much like the first selectors E and E. p v

The connector switch H (Fig. 5) is of the gjeneral type of connector switch shown in nite'd States Letters Patent No. 815,176, granted March 13, 1906, to Keith, Erickson & Erickson. Like the line switches and first selectors it also is arranged to operate in a system in which there is no ground connection at the subscribers station.

A clearer understanding of the operation of my improved system may be had from an explanation of its operation when employed to connect two lines. Furthermore, the cord may be used when any subscriber of the manual exchange desires a connection with a subscriber of the main automatic exchange. The manual exchange operator may operate the automatic oilice switches to establish the desired connection. Furthermore a call coming from the main automatic exchange to the manual exchange may be extended to subscriber of'the manual exchange may be of subscribers 1 connected with a subscriber of the automatic exchange. Suppose that the subscriber of the substation A (Fig. .1) desires connection with the subscriber at substation A (Fig. 5). In that event, when the calling subscriber removes the receiven from the switch hook, an energizing circuit is closed through the trip magnet 53 of the line switch C, said circuit extending from ground G8 (Fig. 1) through the springs 54 and 55, conductor 51, through the receiver and the transmitter to the line conductor'52, springs 56 and .57, through the trip magnet 53, springs 57 and 58 to the battery lead 59, thence through battery B to ground G. As soon as the trip magnet 53 energizes, the armature is attracted, and the plunger is liberated and thrust into the bank terminal. When the plunger enters the bank terminal the relay 31 operates to close the springs 32 and 33 in contact, and thus an energizing circuit is closed through the motor magnet relay 60 which in turn operates to close a circuit through themotor magnet 61 of the master switch D. The motor magnet then operates to advance all idle plungers that are in locked engagement with the plunger shaft to a point opposite the next idle bank terminal similar to the one just engaged. The circuit through the motor magnet relay extends from ground G through the springsv 32 and 33, conductor 34, individual bank segment 35, master switch bank wiper 36, common segment i 37, through the motor magnet relay 60 to the battery lead 59,

thence through battery B to ground G. The

relay 60, upon energizing, operates to place the springs 39 and 40 into contact, whereby a circuit is closed from ground G through the'motor magnet 61, interrupter springs 41 and 42, motor magnet relay springs 39 and 40 to the battery lead '59, thence through battery B to ground G; The motor magnet, upon energizing, attracts its armatu-re 43, and the pawl 44 engages a tooth of the ratchet wheel 45 and moves the latter one step. When this occurs the'spring 46 engages the spring 47, hearing in mind that prior to this operation the spring 46 engages a tooth of the toothed wheel 48; and when the ratchet "wheel 45 is given one step the spring 46 slides oil from the'top of the tooth and engages the spring 47. The engagement of these two springs provides a new energizing circuit for the motor magnet .61, said circuit extending through the springs 46 and 47 to the battery lead 59 instead of through the springs 39 and 40. Furthermore, the motor-magnet, when energized, separates the .interrupter springs 41 and 42, thereby breaking its own circuit in a manner similar to that of a buzzer. The motor magnet- 61 continues to operate in this manner as long as the Sg'filgS 46' and 47 remain in engagement. 1

en the next succeedin tooth on the wheel 48 advances far enoug the spring 47 disengages from the spring 46, thereby opening the energizing circuit for the motor magnet. By the time thls next notch disengages the springs 46 and 47 the master switch wiper 36 has passed from the first contact 35 to the second contact .49. Suppose, however, that when the wiper 36 engages the individual segment 49 there is a guarding potential present. In that event an energizing circuit is closed through the motor ma net relay 60, said circult extending from the contact 49 through the wiper 36, common segment of the master switch bank, through the winding of the relay 60 to the battery lead, as previously traced. The motor magnet relay again energizes and closes the circuit for the motor magnet. The motor magnet operates as before, and the wiper 36 is carried to the next contact, and the next tooth of the wheel 48 separates the springs 46 and 47. This operat on continues as long as the wiper 36 contmues to find contacts with protecting potentials. It will be understood, of course, that y when the motor magnet 61 thus operates, the plunger shaft and all plungers that are in looking engagement with the said shaft are moved to a new position and thereby brought opposite an idle bank terminal similar to the one engaged by the line switch C. At the instant that the plunger enters the bank the following springs are pressed into contact: 62 and 63, 64 and 65, 66 and 67, and 68 and 69. The engagement of the springs 62 and 63 and 68 and 69 extends the calling sub- .scribers line conductors 52 and 51 to the line relay 72 which now restores to normal position. The operator then throws the listening key K to bridge the operators set across the line. The engagement of the bank springs 66 and 67 provides an energizing circuit for the bridge-cut-ofi relay 75 extending from ground G through the springs 66 and 67, through the winding of the bridge-cut-oif relay to the battery, lead 59, thence through battery B and to ground G. The relay 75 energizes and operates to disengage the springs 54 and 55 and 56 and 57, thereby disconnecting the subscribers line conductors 52 and 51 from the line switch C. Also, the engagement of the springs 66 and 67 provides a guarding potential to the private normal conductor 76, thereby protecting the calling line against seizure by some calling subscriber. Furthermore, when the subscribers line conductors 52 and 51 are thus extended to the trunk conductors 70 0 thereby disconnectin and 71, the windings 77 and 78 of the relay 31 are included in the energizing circuit of the line relay 72. The relay 31 energizes and provides a guarding potential at the master switch bank, as stated.

The foregoing operation of the central office mechanism occurs when the calling subscriber removes his receiver from the switch hook and bridges the primary circuit across the line. After getting the number of the desired substation in the automatic exchange the operator inserts the plug 1) in the trunk line jack 7', and throws the key K, so that the springs 79 and 79 engage the s rings 80 and 81,

t e trunk line connection from the cor circuit, and connecting the operators calling device to the trunk line conductors 82 and 83. The trunk line conductors 82 and 83 terminate in the first selector switch E (Fig. 4) of the automatic exchange. When the operators set and calling device are thus bridged across the trunk line, an energizing circuit is established through the line relay 84 of the first selector E. This circuit extends from ground G through the winding 85, side switch wiper 86, conductor 83, rmg of the jack j and plug p, springs 79: and 81 through the receiver and transmitter, impulse springs 87 and 88, springs 80 and 79, tip of the plug 10' and jack j to the conductor 82, side. switch wiper 89, winding 90 to the battery lead 91, thence through battery B and to ground G. The line relay 84 thereupon energizes and operates to carry the spring 92.from engagement with the spring 93 into engagement with the spring 94, thereby providing an energizing circuit for the slow-acting release relay 95 which in turn operates to carry the spring 96 from the spring 97 to the spring 98 before the dial is turned. It Wlll be assumed, for example, that the number of the desired substation is 2220. When the dial returns to normal position for the first digit 2, the first selector switch E is operated. The first digit being 2, the impulse spring 87 is twice carried out of engagement with the impulse spring 88. As a result the energizing circuit through the line relay 84 is broken twice, and the spring 92 comes into contact with the spring 93 twice. After the two impulses are thus delivered the line relay 84 again energizes and carries the spring 92 into contact with the spring 94. As previously! explained, the relay 95 is a slow-acting relaythat is, slow to deenergize; and when this energizing circuit is momentarily broken, during the vertical impulses just delivered the said relay does not deenergize, but remains in an operated position with the springs 96 and 98 in contact. When the spring 92 engages the spring 93 two impulses are transmitted assesses to the vertical magnet 99 the circuit 61b tending from ground through the springs 92 and 93 to the springs 96 and 98, through the private magnet relay 100, through the winding of the vertical magnet 99, contact point 101,,side switch wiper 102 to the battery lead 91, thence through battery B to ground G. Two impulses being delivered, the vertical magnet 99 is thereby energized twice, and the shaft wipers are given two vertical steps in the well known manner. It will be seen that the private magnet relay 100 is included in the energlzmg circuit of the vertical magnet 99. This rela also energizes, but being a slowacting re ay it energizes on the first impulse and remains so until all the impulses are transmitted. This relay, upon energizing, operates'to close the springs 103 and 104 in contact, whereby an energizing circuit is established through the rlvate magnet 105. This circuit extends rom ground G through the s rings 103 and 104, private magnet 105 to tlie battery lead 91, thence through battery B to ground G. The private magnet relay 100 deener izes after the last vertical impulse, since t is energizing circuit is no longer maintained after the springs 92 and 93 disengage. Hence, the said relay deenergizes, permitting the springs 103 and 104 to disengage, whereby the energizing circuit through the private magnet 105 is in turn broken, which private magnet now deenergizes and permits the side switch to pass from first to second position, permitting the side switch wipers 102 and 106 to engage the contact points 107 and 108, respectively. The closure of contact between the side switch wiper 102 and the contact point 107 sets up an energizing circuit for the rotary magnet 109. This circuit extends from ground G through the interrupter springs 110, rotary magnet 109, contact point 107, side switch wiper 102 to the battery lead 91, thence through battery B to ground G. The said rotary magnet then operates to rotate the shaft wipers 111, 112 and 113 of the selector E into engagement with the first contact of the second level-of the selector banks, from which contact it is assumed the trunk line conductors 114, 115 and 116 lead to the second selector. switch F. If the first trunk line is busy, however, and the wipers have to pass over busy trunk lines, then as soon as the private wiper 113 engages the first private bank contact the private magnet 105 again energizes, locking the side switch in second position. The energizing circuit for said private magnet extends from the grounded terminal of the battery B, through an occupying switch (not shown), through the private wiper 113, thence through the conductor 117 to the side switch wiper 106, contact point 108, through the winding of the private magnet 105 to the battery lead 91, I

- thence through battery B to ground G.

The private magnet 105 u on thus becoming energized, locks the siile switch wiper 102 in'engagement with the contact point 107, whereby the rotary magnet 109 will be energized step by step until the wipers are carried beyond the last busy trunk line. At the instant that the private wiper leaves the last busy contact point the energizing circuit through the private magnet 105 is destroyed, and as a result the selector side switch passes to third position. If, however, there are no busy trunk lines, the pri vate magnet 105 releases the side switch to third position as-soon as the wipers are carried into engagement with the first trunk line. As soon asthe side switch passes to third position, as stated, the trunk line conductors 82 and 83 are extended to the conductors 114 and 115 which in this case, it is assumed lead to the second selector switch F. The extending of the line occurs,

of course, as soon as the side switch wipers 89 and 90 engage the contact points 118 and 119, respectively. When'the trunk line is thus extended to the selector switch E an energizing circuit is established through the line relay 120 in the samemanner in which the energizing circuit was established through t e line relay 84 of the selector spring 126 to the spring 127, and the springs 128 and 129 are closed in contact.

This operation of the second selector switch F occurs at the instant that the side switch wipers 89 and 86 of the selector switch E pass to third position and extend the trunk line conductors 82v and 83 to the second selector switch F. When the second selector switch is thus operated, a guarding potential is established at-the private wiper 113, for protecting the seized trunk line conductors 114 and 115 against seizure by another calling first selector. This guarding potential extends from ground G to the contact point 130, side switch wiper 131,.

through the springs 129 and 128, conductor 116 to the contact engaged by the er izing circuit is established through the reease relay 95. This energizing circuit 7 rivatewiper 113. Furthermore, when therstis'e" lector, switch E operates, and the side switch passes to third position, a new enextends from ground G at the selector switch F, through the springs 129 and 128, conductor 116, shaft wiper 113, conductor 117, through the side switch wiper 106, contact point 133, through the relay 95, thence through battery B to ground G. The relay 95 thus remains in an operated position, with the spring 96 in engagement with the spring 98, but the line relay 84 returns to normal position when the side switch wipers 89 and 86 engage the contact points 118 and 119, respectively. The energizing circuit through the line relay 120 extends from ground G through the. Winding 134 to the side switch wiper 135, thence through the conductor 115, conductor 83, and through the primary circuit of the operators set, through the trunk conductor 82, conductor 114, side switch wiper 136, through the winding 137 ofthe relay 120 to the battery lead 91, thence through battery B to ground G. hen the dial returns to normal position for the second digit 2 this circuit through the line relay 120 is interrupted twice, when the impulse spring 87 is carried out of engagement with the spring 88 by the impulse teeth on the wheel 138. The circuit being. interrupted twice, the said relay 120 momentarily denergizes, thus permitting the spring 121 to engage the spring 122, whereby, an energizing circuit is completed through the vertical magnet 139,-said circuit extending from ground G to the springs 121 and 122, springs 125 and 127, through the winding of the private magnet relay 140, through the winding of the vertical magnet 139, contact point 141, side switch wiper 142 to the batter lead 91, and through battery B to round The private magnet relay 140 eing included in this circuit energizes, and since it is a slow-acting relay it remains in an operated position until the last vertical impulse is delivered, and the relay 120 remains energized, with the'spring 121 in contact with the spring 123, whereby the circuit through the private magnet relay and the vertical magnet 139 remains open. When the relay 140 energizes, the springs 143 and 144 are pressed intocontact, thereby causing an energizing current to flow through the private magnet 145, the circuit extending from ground Cr through the springs'143 and 144, through the winding of the private magnet 145' to the battery lead 91 thence through battery B to ground G. When the relay 140 denergizes and breaks -the energizing circuit through the private magnet 145, the private magnet also 'deenergi ze sE-and permits the side switch to pass from first to second position. When the side ,switch wiper 142 passes to second position,

andinto engagement with the contact point 146, an energizing circuit is established through the rotary magnet 147, which now operates, as explained in connection with the rotary magnet 109 of the selector switch E, to select an idle trunk line leading to the connector switch. After the switch comes to rest, with the side switch in third position, the shaft wipers 148,149 and 150 are in engagement with the trunk conductors 151, 152 and 153, respectively, which lead to the connector switch H (Fig. 5). At the lnstant that the side switch wipers 136 and 135 pass to third position, inengagement with the contact points 154 and. 155, the trunk line conductors are extended to the connector switch H and an energizing circuit is established through the line relay 156 in' the sanie.

manner in which the energizing circuit was established through the line relay 120 of the selector switch F when the side switch wipers of the first selector passed to third position. The energizin circuit through the line rela- 156 extends rom ground side switc wiper 157, conductor 158, through the winding 159 trunk conductors 152,115 and 83, thence through the operators set to the trunk conductors 82, 114 and 151, thence through the winding 160 to the battery lead 91, and

through battery B to ground G. The line relay 156, upon energizing, operates to shift the spring 161 from the spring 162 to the spring 163, whereby an energiz ng circuit is established through the release relay 164, said circuit extending from ground G through the springs 161 and 163, rela 164 to the battery lead 91, thence throng battery B to ground G. When the relay 164 energizes, the spring 165 is shifted out of contact with the spring 166 and into contact with the spring 167, and the spring 168is shifted into engagement with the spring 169. This primary operation of the connector relays 156 and 164 occurs at the instant that the side switch wipers 136 and 135 of the selector F pass to third position and extend the trunk line conductors to the connector H. The engagement of the springs 168 and 169 establishes a guarding potential for protecting the trunk line conductors 151, 152 and 153 against seizure by another line and second selector. This potential extends from ground G to the side switch wiper 165, springs 168 and 169, conductor 153 to the private bank contact engaged. by the shaft wiper 150. Furthermore, when the side switch of the second selector F passes to third position anew energizing circuit is established through the release relay 124, said circuit extending from ground G at the connector switch H (Fig. 5), through the springs 168 and 169, conductor. 153, shaft wiper 150, conductor 170, side switch wiper 171, through the relay 124 to the battery lead 91, thence through battery B to ground G. The operation of the dial for the last. two digits affects the connector switch, and when the dial is operated for the thlrd digit 2 the impulse spring 87 is twice carried out of engagement with the spring 88, thereby momentarily deenergizing the line relay 156 twice, whereby the s ring 161 twice engages the spring 162 t us sending two impulses to the vertical magnet 172 from ground G through the springs 161-and 162, springs 165 and 167, through the vertical magnet 172, contact point 173, side switch wiper 174, private magnet relay 175 to the battery lead 91, thence through battery B to ground G. The private magnet relay 175 energizes when the first impulse is delivered, and since the said relay is slow-acting it remains in an operated position until all the vertical impulses are sent. The vertical magnet,.upon being energized, operates one step at a'time to carry the shaft wipers 176, 177 and 178 two steps to a point opposite the second level. .The relay 17 5, upon energizing, shifts the springs 179 and 180 out of engagement, and the spring 180 is shifted into engagement with the spring 181. When the springs 180 and 181. engage, an energizing circuit is established through the private magnet 182 from ground G through the springs 180 and 181, private magnet 182 to the battery lead 91, thence through battery B to ground G. The relay 17 5, being a slow-acting relay, remains in an operated position while the vertical impulses are being sent; but after all the impulses are delivered, and the line relay 156 returns to its operated position, the circuit through the relay 17 5 becomes broken, thus permitting the spring 180 to return to normal position. When the springs 180 and 181 disengage, the circuit through the private magnet 182-becomes broken, whereby the said magnet denergizes, permitting the side switch to pass from first to second position, thus putting the line relay in control of the rotary magnet through the side switch wiper 174 and contact point 186. The operator now operates the calling device for the last digit 0, thereby transmitting ten impulses and operating the line relay 156 ten times. Each time that the line relay springs 161 and 162 engage, an energizing circuit is established through the rotary magnet 183, said circuit extending from ground G through the said springs 161 and 162, springs 165 and 167, springs 184 and 185, through the rotary magnet 183 to the contact point 186, thence through the side switch wiper 174, through the private magnet relay175 to the battery lead 91, thence through battery relay energizes, as in the previous case, remaining so until all the impulses are transmitted, thereby retaining the private magnet also energized. The rotary magnet 183 then operates to rotate the shaft wipers into engagement with the desired line #2220. If this line is busy at the time, the side switch will be locked in second position in the man- B to ground G. Again the private magnet 1,see,aso

description of how a connection is estab lished will be completed. As soon'as the line relay 156 ceases to operate for the last digit, the private magnet relay 175 deenergizes, as heretofore explained, in this instance permittin the side switch to trip to third position. The result is that the side switch wipers respectively engage their conlamp 24. Of course,

tact points in the third position. When the side switch wiper 157 engages the contact point 187 a guarding potential is completed at the private wiper 178 for protecting the seized line from outside interference while the connection is established. This guarding potential extends from ground G through the side switch wiper 157, springs 188 and 189 to the private wiper 17 8. Not only does this guarding potential prevent other connectors from calling in on the same line over multiples of the normal conductors 190 and 191 and 192, but it also provides means for energizing the cut-ofl relay 193 of the line switch C whereby said switch C is prevented from operating when the called subscriber removes his receiver 194: from the switch hook 195. When the side switch operates and passes to third position, ground G is disconnected from the trunk conductor 153, and a guarding potential is provided from ground G as follows: When the side switch wiper 157 passes to third position the short-circuit of the relay 196 is removed, also the ground for the line relay circuit. The ground G is thereby substituted, and the relay 196 energized in series with the windings of the line relay 156. The relay 196 closes the springs 193 and 194 in contact, thereby providing a guarding potential from ground G through the springs 193 and 194: to the contact point 197, side switch wiper 165 springs 168 and 169 to the conductor 153, then to the bank contact engaged by the wiper 150. The object of the relay 196 is to enable the operator at the manual exchange to obtain supervision, which is accomplished as follows: Normally, after the operator makes a call and the side switch passes to third position, the key K is re-' stored, thereby disconnecting the calling device from the line conductors and bridging the supervisoryv relay 22 instead. The supervisory relay 22 is so arranged that when included in a series circuit with the windings 159 and 160 of the line relay 156 of the connector, the said relay 22 energizes and attracts its armature from the lamp contact point; but when the relay 196' is also included in the circuit with the supervisory relay 22" and the windings of the line relay, the relay 22 does not remain in an-operat1ve position, but permits its armature to engage the lamp contact point, thereby completing a circuit through the supervisory lamp 24:. When the called subscriber answers, the relay 196 is short-circuited, and consequently the supervisory relay 22 is operatively energized. However, when the called subscriber restores his receiver the relay 196 again enters the circuit, and the relay 22 restores to its normal position, closing a circuit through the supervisory when the side switch wipers 197 and 198 engage their third-position contact points 199 and 200, the line is placed in connection with the called subscribers line, over the heavy conductors shown, the circuit passing through the ringer-relay springs 201 and 202 on one side, and 203 and 204 on the other side. As soon asconnection is thus established, and when the side switch wiper 174 engages the contact point 206, the energizing current flows from ground G at the ringer interrupter, through the back-bridge relay springs 208 and 209, ringer relay 205, conductor 210, contact point 206, side switch wiper 174 to the battery lead 91, thence through battery B to ground G. It will be seen that the energizing circuit of the ringer relay 205 will be broken periodically, so as not to ring the called subscriber continuously. Furthermore, it will be seen that each time that the ringer relay is energized, the springs 201 and 203 are separated from the ringer relay springs 202 and 204, thereby separating the calling line from 'the called line, and pressing the springs 201 and 2 03 onto the springs 211, and 212' which are the terminals of the ringer generator I. As a result ringing current is sent over the called line for energiz ing the bell 213 while the springs 214 and 215 are in contact. However, as soon as the called subscriber answers, the back-bridge relay 216 is energized by a flow of current from ground G side switch wiper 157, winding 217 of the back-bridge relay 216, ringer relay springs 204 and 203, side switch wiper 198, contact point 200, line wiper 17 7, normal conductor 191, conductor 218, springs 215 and 219, impulse springs 220, primary winding 221, transmitter 222, line conductor 223, normal conductor 190, line wiper 176, contact point 199, side switch wiper 197, ringer relay springs 201 and 202, winding 224 of the back-bridge relay 216, thence to the battery lead 91, and

energize as long as the called subscriber is on, the line. Furthermore, when the relay 216 energizes, the springs 225 and 226 enage, thereby short-circuiting the relay 196. in the meantime the operator restores the key K ,to normal position, thereby extendlng the calling subscribers line and trunk conductors to the outgoing trunk line, to which latter is connected the desired substation #2220. The calling subscriber is provided with talking battery current from the cord circuit 0 through the supervisory relays 21 and 22. The subscribers being thus connected, they may communicate over the mam talking conductors indicated by the heavy lines in Figs. '1, 2, 4 and 5, including the condensers 227, 228 and 229 on one side, and on the other side the condensers 230, 231

and 232. After the subscribers are through.

talking, if the calling subscriber hangs up his receiver he opens up the line circuit, and the circuit including the two supervisory relays 21 and 22 in the series with the primary circuit is broken. The relay .21 denergizes, but the relay 22 remains energized, since a circuit is maintained from the ground at the cut-ofi' relay 74. A circuit is therefore completed through the supervisory lamp 23, in-

dicating to the operator that the trunk line conductors 70 and 71 have been abandoned.

Furthermore, when the subscriber at sub-' magnet 34 to the battery lead 59, etc. The

release magnet then energizes and remains in readiness to withdraw the plunger from the bank terminal when the energizing circuit is broken by the relay 236 which is included in the circuit with the release magnet. The calling subscriber at substation A thereby restores the line switch C, and the trunk line remains in readiness to be used by some other subscriber.

plained, now restores to normal position,

permitting its armature to close the circuit through the supervisory lamp 24, thereby giving the operator the diswnnectusi gnahj is then withdrawn from the. .I jack j, whereby the circuit including the- The plug p windings of the line relay 156 and the relay 196 is broken. Therelay 196, upon deener- --1s restored also. I

gizing, separates the springs 193 and 194, thereby in turn breaking the energizing circuit for the slow-acting release relay 164.

234 is closed at a point between the Springs 161 and 162 and at another point between the springs 165 and 166. A flow of current is, therefore, set up from round G through the springs 161 and 162, t rough the springs 165 and 166, release magnet 234 to the off normal spring 2%, contact point 236 to the battery lead-91, thence through battery B to ground G. The release magnet instantly releases the connector switch shaft and restores the side switch thereof. As soon as the connector switch shaft reaches its lowest position it breaks the circuit for the release magnet 234 by separating the off normal spring 235 from the contact point 236, at which instant the release magnet of the connector-is also restored. The

operation of theline relay 156 and of the slow-acting relay 164 not only causes the release of the connector, as described, but also the release of the preceding switches, because the ground connection from ground G to the trunk-release conductor 153 is interrupted by the relay 196. Since the release relays 95 and 124 of the selector switches are dependent upon this ground for their energized condition, as already explained, it follows that they will fall back, with the following results: As soon as the release relay 124 of the second selector F deenergizes, the spring 125 falls back into normal engagement with the spring 126, thereby closing an energizing circuit for the release magnet 237, said circuit extending from ground Gr through the springs 121 and 122, through the springs 125 and 126, release magnet 237, thence to the contact point 238, of]? normal spring 239to the battery lead 91, thence through battery B to ground G. As soon as the release magnet 237 energizes, the second-selector side switch and switch shaft are restored, which switch When the called subscriber restores his shaft, upon reaching its lowest position, opens up a release circuit at a point between the off normal spring 239 and the contact int 238, whereb the release magnet 237 en the release relay 95 of the selector E denergizes, the springs 96 and 97 are brought into contact, and as a result the energizing circuit for the release magnet 240 is closed. The energizing current for this release magnet'240 then flows "from ground Gr through the springs 92 and I 93, and'through the said springs 96 and 97 to the release magnet 240, thence through said ,-1 nagnet to the contact point 241, off

normalspring 242 to the battery lead91,

thence through battery B to ground G. The release magnet, upon energizing, then restores the first selector side switch and switch shaft, which switch shaft, upon reaching its lowest position, opens the energizing circuit for the release magnet 240 at a point between the off normal spring 242 and the contact oint 241. Thus it will be seen that the cailing subscriber, in re storing his receiver, releases his line switch from the trunk connection, and also gives the operator the disconnect signal. In'restoring his receiver the called subscriber gives the operator the disconnect signal, and when the plug 12' is removed from the jack j the central ofiice switches of the automatic exchange are released and restored to normal, as explained.

Referring now to that stage of the call a where the operator was operating the connector switc in accordance with the last digit 0, it will be explained what takes place in the event that the desired line is busy. When the line #2220 iscalling, or when 1t has been called by someone else, the private bank contacts in which the normal conductor 192 terminates are connected to ground. If another connector switch has called the line, this ground potential would be supplied through the connector switch from a ground terminal similar to the g rIound termi-. nal G in the connector switch as alread explained; but if the line switch 0 is cal ing, a guarding potential is established from the line switch bank ground (as in Fig. 1) to the private bank contact. In a similar manner the line switch C protects the calling line A, when the bank springs 66 and 6 come into contact, from ground G. From this ground connection is established through the said bank springs to the private normal conductor 76. Therefore, when the subscriber sends in the last impulse the private Wiper 178 is carried onto the grounded contact, and when the slow-acting relay 175 of the connector deenergizes, instead of the side switch tripping to third position, as in the case where the line is notbusy, the side switch is locked as follows: The private magnet 182 is prevented from deenergizing, because it is connected with the private wiper 178 at the time over the following circuit: from the private wiper 17 8 to the lockin spring 189, thence to the spring 188, and t rough the-winding 217 of the back-bridge relay 216 to the talking line conductor 243, thence through the ringer relay springs 204 and 203 to the side switch wiper 198, contact point 244 (the side switch being in second position), through the private magnet 182 to the battery lead 91, thence through batte B to ground G. The private magnet there ore remains energized, retaining the side switch insecond position. It will be seen that at the same time the backbridge relay 216 energizes in series with the private magnet 182 over the circuit from the following circuit: from ground G through thence to the private wiper r178. Therefore, the backbridge relay 216, upon energizing, presses the springs 245 and 246 into contact, thereby energizing the locking relay 247 over the the slow-acting relay springs 180 and 179, through the private ma net springs 248 and 249, through the said relay 247, and through the back-bridge relay springs 245 and 246 to the battery lead 91, thence through battery B to ground G. It will be seen that when the relay 247 energizes, the connection between the rotary magnet 183 and the spring 167 is broken at a point between the springs 184 and 185. The object of this arran ement is to prevent the calling subscri r from further rotating the connector switch, if he should attempt to operate his dial while receiving the busy signa -that is, while the connector switch is locked in second position. It will also be seen that when the relay 247 energizes, the circuit for maintaining the private magnet 182 energized is shifted from the private wiper 178 to the sprin 250, which latter is connected to groun G The ob'ect of this arrangement is to prevent the side switch from unlocking and passing to third position, if the switch that is maintaining the called line busy should be released while the calling subscriber A (Fig. l) is receivin the busy si a1. It will be evident that i? the ground 5 were not substituted for the ground at the private wiper 178, the private magnet 182 would deenergize if the switch that is sup lying ground at the private wiper 17 8 shou d release, and this, of course, would be undesirable. It will also be seen that the relay 247, upon energizing, closes the s rings 251 and 252 in contact, thereby esta lishing the busy cir-' cuit as follows: from the rimary winding of the busy coil 253 through the springs 252 and 251 to the second-position slde switch contact point 254, side switch wiper 197", ringer relay springs 201 and 202, through the condenser 229, conductors 151, 114, 82,

70 and 52, through the substation A to the other side of the line, then over that side back to the connector H, and through the winding 159 of the line relay 156 to ground,

interrupter ground G, through the interrupter 264 to the primary winding of the busy coil 253 back to the secondary winding. When the calling subscriber receives the busy signal he understands that the line is busy and hangs up his receiver. The operator is given the disconnect signal, as before, when the line switch C is restored. The plug p is removed from the jack j, and the automatic central office switches are released, as heretofore explained. It will be seen, of course, that as soon as the side switch is restored the energizing circuit for the back-bridge relay 216,

which includes the winding 217 thereof, and

for the private magnet 186 is broken whenthe side switch wiper 198 leaves the contact point 244. Now, since the energizing circuit of the locking relay 247 is controlled by the back-bridge relay 216, the said locking relay is also denerglzed, and the connector switch is left in anormal condltion.

In the foregoing it has been shown how a manual exchange substation may be connected with an automatic exchange substation through the means of the cord circuit 0. It will now be pointed out how an automatic exchange subscriber may receive connection with a manual exchange subscriber. First, it should be explained, however, that the arrangement of the manual statlons 1s somewhat different from the ordinary-that is, the lines of the substations terminate in line switches, just as do the lines of the automatic stations. Usually one hundred of these lines with their respective line switches are arranged in one group, and in each group the said switches are controlled by a master switch. To each of these groups, there are allotted a number of trunk lines, usually ten in number. These trunk lines terminate at the switchboard, and all outgoing calls are made over these trunks. For incoming calls to a group of stations there are allotted connector switches each of which is adapted to make connection with any one of the lines of the group to which it is allotted. The terminals of this connector switch extend to a jack in the manual board, and may be operated as desired by the operator. Suppose, for example, that an automatic subscriber,

' as at substation A ig. 3), wishes connection with the manual substation A (Fig. 1). From the first level of the first selector banks it will be assumed that trunk lines lead to the manual switchboard. Hence, when a subscriber at an automatic subscribers station operates a first selector switch for the digit 1, a trunk line is seized leading to the manual switch-board. The operator then takes up the call from the trunk line, and by means of a calling device operates a connector to seize the desired line. In this instance, when the receiver 2 is removed from the switch hook 3 (Fig. 3) the line switch C is o erated to seize an idle first selector switch The dial is then turned for the digit 1, and the selector E operates in the usual manner to select an idle trunk line the conductors 254 and 255 of which terminate in the jack 3' (Fig. 2).- When the conductors are thus seized an energizing circuit is closed through the line relay 256, which operates and gives the signal in the usual way. The operator inserts the plug 17 into the jack jfland upon learning that connection with substation A is desired inserts the plug 2' into the ack i allotted to the connecter switch H (Fig. 1), which is adapted to make connection with subscribers lines of the group of which A is a member. The connector switch H, which is a duplicate-of the connector switch H (Fig. 5), is operated in the usualmanner to connect with the terminals of the normal conductors 257, 258 and 76 of the line of station A. The calling and called subscribers stations are provided with talking battery current in the usual manner, and when the receivers are restored to their switch hooks the operator is given the disconnect signal as before. The plugs 10 and p are removed from the jacks j and j and the switching apparatus restored. An automatic subscriber at substation A desiring connection with an auto- 'matic subscriber A (#2220, for example) removes the receiver from the hook, and selects an idle first selector E which is operated to select an idle second selector F (Fig. 4) when the dial is turned for the first digit 2. The second selector F is then operated to extend the connection to a connector switch H, which is operated when the dial is turned for the last two digits to extend the connection to the normal conductors of the desired line. The selector and connector switches are operated in the manner explained, and when the calling subscriber at substation A restores his receiver to the switch hook, the energizing circuit through the line relay is broken and the switches are released. A manual subscriber maycall another manual substation by means of the operator and the cord 0, as is well known.

Thus, it will be seen that any subscriber of the automatic exchange may call any other automatic substation direct, and by operating a selector switch to a certain level connection is established with a manual switchboard, from which connection may then be extended to any manual subscriber; also, any manual subscriber may be extended to any manual or automatic exchange subscriber. In each'case where the call goes through the manual board and cord 0 the operator is given supervision over both calling and called lines. In regard to the action of the line relay 156 of the connector H (Fig. 5) it may be said that this relay will restore to normal position when the relay 196 is included in the circuit with the supervisory relay 22 and the windings of the relay 156, if the relay. 196 has a sufiiciently high resistance. If the relay 156 does return to normal position it has no efl'ect at this time, because the energizing circuit through the release relay 164 is then maintained from ground G through the springs 193 and 194*, contact point 197 and relay 175 to the battery lead 91, thence through battery B to ground G. Thus, it is immaterial whether the relay 156 remains operatively energized or restores to normal when the relay 196 enters the circuit.

The relay 263 (Fig. 3) performs the same function when an automatic substation calls a manual substation as do the springs 168 and 169 of the relay 164 F1g. 5) when the manual substation calls the automatic sub-. station. It is the function of the relay 263 to supply ground for holdin the slow-acting' release relay 257 of the rst selector E in an energized condition during conversation. The relay 263 energizes as soon as the side switch of the first selector E passes to 'the third position. The circuit through the rela 263 extends from ground G? over the con uctor 254, through the winding 258 of the relay 263, through the substat1on A,

back through the winding 259, conductor tery B. As soon as the subscriber at substation A restores his receiver to the hook, the

energizing circuit of the relay 263 is destroyed, the contact between the sprin s 260 and 261 is opened, and the selector releases in the manner described in connection with the selector E.

From the foregoing it will be seen that I provide means whereby a manual swltchboard operator may efliciently supervise all connections established through the medium of the manualboard. in a system in which the automatic switches are controlled over the two sides of the line circuit in series, there being no operating grounds at the substations of the automatic subscribers. It will also be seen that I provide means whereby a line switch may seize a two-conductor trunk line, or whereby a selector ma seize a two-conductor trunk line, and w ereby these switches may be released at the proper time, notwithstanding that neither trunk line has the usual third conductor over which the release is ordinarily accomplished. In this way efficient service is provided between manual and automatic subscribers in a system in which the automatic switches are controlled over the two sides of the line circuit in series.

It will also be seen that my improved semi-automatic system is applicable to a system of that character in which the automatic subscribers are divided into groups, 'say ten in each group, and in Which the connectors have vertical motion to select groups and then rotary motion to find the called line in any selected group. The ten groups of ten levels in any connector go I to kick The hol mg resistance relay to permit the operation of make up the larger group of one hundred subscribers. Thus, each subscriber is a member of a certain hundred group, and is also a member of a sub-group of ten. The trunks are also divided into groups,-so that the selectors have vertical motion to select cups and then rotary motion to automatical find an idle trunk in any selected group. hese selectors and connectors are, as stated, controlled over the two sides of the line circuit in series, there being no operating grounds at the automatic substations, or at the manual board where the operator is provided with a calling device, for controlling the automatic exchange e uipment.

What I c aim as my invention is 1. In a tele hone system, a manual switchboard, a trunk leading to said board, means whereby a calling subscriber automatically seizes said trunk, a trunk leading from said board, means controllable by the operator at said board for extending connection from said last-mentioned trunk 1n the direction of a called subscriber, a cord circuit for connecting said trunks, a single supervisory relay in a bridge across said cord circuit, means for causing said relay to energize when the called subscriber answers, and a supervisory signal responsive to the deenergizing of said relay, adapted to be retired by the energizing thereof. I 2. In a telephone system, a cord circuit supervisory relay, a connector provided with a line relay havi a winding adapted to be connected in serles with said supervisory relay, a hi h resistance relay adapted to be connecte in series with said other relays, means for short-circuiting said high said line relay, means for removing said short-circuit, when the called line is found, to prevent'said supervisory relay from energizing, means for causing said relay to energize when the called subscriber answers, and a supervisory signal controlled by said supervisory relay.

3. In a telephone system, a called line, means for finding the called line to form a talking circuit, an operators supervisory relay bridged across the talking circuit, a pair of line relay coils, a battery adapted to be connected in series with said supervisory relay over a circuit including portions of the two sides of the talking circuit, a high resistance relay in said circuit, means for short-circuiting said high resistance relay, before the called line is found, to permit the operation of said line relay coils, means for removing the short-circuit, when the called line is found, to prevent said supervisory relay from energizing, and means for causing said supervisory relay to energize when the called subscriber answers, together with a supervisory signal controlled by said supervisory relay.

tor trunk line adapted to be seized by said selector, and a relay at the end of the trunk line adjacent the selector, adapted to be energized over the two sides ot'the trunk line to maintain the first-mentioned relay energized until a release isdesired.

5. In a telephone system, a llne switch provided with a release magnet, a trunk adapted to be seized by said line switch, a relay for the end of the trunk adjacent the line switch, adapted to be energized over the two sides of the trunk, means for establishing a guarding potential for said trunk by the energizing of said relay, and means for energizing said release magnet by the deenergizing of said relay.

6. In a telephone system, a selector provided with a relay necessarily energized during talking, release mechanism operated when the said relay is deenergized after the subscribers are through talking, a two-conductor trunk line adapted to be seized by said selector, and a relay at the end of the trunk line adjacent the selector, adapted to be energized over the two sides of the trunk lin to maintain the first-mentioned relay energized until a release is desired, said trunk provided with a condenser in each side thereof, as and for the purpose set forth.

7. In a telephone system, a line switch provided with a release magnet, a trunk adapted to be seized by said line switch, a relay for the end of the trunk adjacent the line switch, adapted to be energized over the two sides of the trunk, means for establishing a guarding potential for said trunk by the energizing of said relay, and means for energizing said release magnet by the denergizing of said relay, said trunk provided with a condenser in each side thereof. as and for the purpose set forth.

8. In a telephone system, subscribers lines, trunk lines, suitable automatic switches for extending connection over said trunk lines from a callin to a called subscriber, a side switch an a line relay for said automatic switches, means controlled by said line relay for placing a guarding potential on a busy trunk, and parallel connections for maintaining said busy connection when said line relay is deenergized.

9. In a telephone system, subscribers lines, trunk lines divided into groups, suitable automatic switches for extending connection over said trunk lines from a calling to a called subscriber, said switches having ve tical motion to-select groups and rotary motion to find a line in a selected R group, a side switch and a line relay for said automatic switches, means controlled by said line relay for placing a guarding potential on a busy trunk, and parallel connections for maintaining said busy connection when said line relay is deenergized. 10. In a telephone system, subscribers lines, trunk lines, suitable automatic switches for extending connection over said trunk lines from a calling to a called subscriber, a relay for said automatic switches adapted upon energization to place a guarding potential on a busy trunk, and parallel connections for maintaining said busy connection when said relay is denergized.

11. In a telephone system, subscribers lines, trunk lines divided into groups,

suitable automatic switches for extending connection over said trunk lines from a calling to a called subscriber, said switches having vertical motion to select groups and rotary motion to find a line in a selected group, a relay for said automatic switches adapted upon energization to place a guarding potential on a busy trunk, and parallel connections for maintaining said busy connection when said relay is deenergized.

12. In a telephone system, subscribers lines, trunk lines, suitable automatic switches for extending connection over said trunk lines from a calling to a called subscriber, and means for placing a busy potential on a tru k over parallel circuits, whereby one of said circuits may be broken without destroying 'said busy condition.

13. In a telephone system, subscribers lines, trunk lines divided into groups, suitable automatic switches for extending connection over said trunk lines from a calling to a called subscriber, said switches having vertical motion to select groups and rotary motion to find a line in a selected group, and means for placing a busy potential on a trunk over parallel circuits, whereby one of said circuits may be broken without destroying said busy condition.

14. In a telephone system, subscribers lines, a manual link, trunk lines, means for establishing a talking circuit between a ing circuit including said manual link and a plurality of'said trunk lines, an automatic progresslvely movable switch individual to each trunk line, a line relay individual to each switch operated over the two sides of the talking circuit in series for controlling said switch, and means associated with said manual link for supervising said connection.

16. In a telephone system, subscribers lines, a manual link,'trunk lines, means for establishing a talking circuit between a calling and a called subscribers line, said talking circuit including said manual link and a plurality of said trunk lines,- an automatic progressively movable switch individual to each trunk line, a line rela individual to each switch operated over t e two sides of the talking circuit in series for controlling said switch, a signal, and means whereby said signal is displayed when saidcalled' line is found and retired when the called subscriber responds.

17. In a telephone system, subscribers lines, trunk lines, a manualoperators position for extending a talking circuit including a plurality of said trunk lines fromla over two sides of a line circuit inseriesto v control said sw1tch, and a signal at said op--- calling lineto a called line, an automatic progressively movable switch individual to each trunk line a relay individual to each switch,

and means for energizing said relay over two sides of said talking circuit in series to control said switch, and meansat said manual operators position for supervising said connection.

18. In a telephone system, subscribers lines, trunk lines, a manual operators position for extending a talking circuit from a calling line to a called line including a plurality of said trunk lines, an automatic progressively movable switch individual to each of said trunk lines, a relay individual .to each switch, means for energizing each relay over the two sides of the talking circuit in series to control its associated switch, a signal at the operators position, and means whereby said signal is displayed when the called line is found and retired when the called subscriber answers.

19. In a telephone system, subscribers lines, suitable automatic means, trunk lines.

divided into groups, a manual operators position for extending connection from a calling line to said automatic means for completing said connection to a called line, said automatic means including an automatic switch having vertical motion to select groups and rotary motion to find a, line in aselected group, a magnet individual to said switch, means for energizing said magnet erators position adapted to be displayed when thecalled line is found and when the called subscriber answers;-

manual operators position for extending a of said trunk lines, suitable automatic means associated with each trunk line for com leting said connection to a called line, sai automatic means including an automatic switch having vertical motion to select groups and rotary motion to find a line in a selected group, a magnet individual to said switch,

means for energizing said magnet over two sides of said talking circuit in series to control said switch, and means at said manual operators posltion for supervising said connection.

net over two sides of the talking circuit in series to control said switch, a relay bridged across said cord circuit, and a signal controlled by connection.

22. In a, telephone system, subscribers lines, trunk lines divided into groups, a manual operators cord circuit and suitable automatic means for extending connection from a calling to a called subscribers line, said automatic means including anautomatic switchhaving vertical motion to select groups and rotary motion to find a line in a selected group, a magnet individual to said switch for controlling the operation thereof, means for energizing said magnet over two sides of a line circuit in series, a relay bridged across said cord circuit,'and a signal controlled bysaid relay adapted to be displayed when the called line is found and retired when the called subscriberanswers.

23. In a telephone system, subscribers lines, a manual operators position,-trunk lines extending from said subscribers lines to said operators position, switches individual to said subscribers lines for selecting an idle trunk line, automatic means in-. cluding suitable automatic switches for extending connection from said operators position to a called subscribers line, a supervisory device-bridged directly across the line at said operators position for supervising said connection anda battery for operating said supervisory device, said battery excluded from said bridge.

24,, In a telephone systemfsubscribers lines trunk lines divided into groups, a r ire-11 manual" operators position, switches individual to said subscribers lines for select- 20. In a telephone system, subscribers? lines, trunk lines divided into groups, a"'

ingtagidle trunk line extending to said operators: osi'tion, automatic means including automat c switches controllable .by an o erator over two sides of a line circuit in said relay for supervising said when the called subscriber answers.

. the, called subscriber answers.

-means controlled over two sides ofthe talkseries and having vertical motion to select In. a telephone system, a manual groups and rotary motion to find a line in switchboard, a trunk leadlng to said-board, the'selected group for extending connection an automat1c progresslvelymovable switch from said operators position to a called subunder the control of a callmg subscriber for scribers line, and means at said operators automatlcally selzlng said trunk, a trunk position adapted to be displayed when the leadlng from sald board, an automat1c procalled line is being found and retired when gresslvely movable switch under the control of the operator at said board forextendlng 25. In a telephone system, a manual connection from said last-mentioned trunk switchboard, an automatic switch, an imin the direction of a called subscriber, a pulse transmitting device; controllable ,by cord circuit forconnectlng said trunks, a the operator at said board for o erating' single supervisory relay in a bridge across said switch over two sides of the tal ing cirsaid cord circuit, an electromagnet for causcuit in series for completing connection from n Said relay rg When file called a manual line to an automatic line, a dial Su scriber answers, and a supervisory slgnal for controlling said impulse device for sendresponsive to the deenergizingof said relay, ing a variable number of impulses dependadapted to be retired by the energizing ing upon the number of the called line, and 1 thereof.

30. In a telephone system, a cord circuit ing circuit for giving the operator a signal supervisory relay, a connector provided with a line relay having a winding adapted to 26. In a telephone system, a manual be connected in series with saidsupervisory switchboard, jacks onsaid board, a cord cirrelay, a high resistance relay adapted to be cuit for connecting one jack to another to connected in series with said other relays, an extend connection from a calling manual auxiliary automatic switch for short-circuitline in the direction of the called automatic ing said high resistance relay to permit the line, an automatic switch, an impulse transmitting device controllable by the operator at said board for operating said switch over two sides of the talking circuit in series for completing the connection, a dial for controlling said impulse device for sending a variable number of impulses depending upon the number of the called line and a signal on the board controlled over two sides of the talking circuit to indicate when the called subscriber answers.

27. In a telephone system, a manual switchboard, trunk-lines, means including said manual board for establishing a talking circuit between a calling manual subscriber and a called automatic subscriber, said talking circuit including a plurality of said trunk lines, an'automatic switch individual to each of said trunk lines, means on said board controlled over the two sides of the talking circuit for supervising such connection, and means whereby the automatic switches used in making the call are controllable over the two sides of said talking circuit in series.

28. In a telephone system, an operators cord circuit, a bridge.of said cord circuit including a calling device, trunk lines'accessible to said cord circuit, automatic switches individual to each line, a line relay for each, switch, each energized over-a circuit including said trunk lines and said bridge in series, and controlled by the operation of said calling device to, operate said switches successively to extend a connection from said cord circuit, and meansin the cord circuit controlled over the two sides of said trunk lines in series for supervising said connection.

- operation ofi said line relay, a magnet for operating said auxiliary switch for removing said short-circuit, when the called line is found, to prevent said supervisory relay from energizing, a relay controlled by the called subscriber for causing said supervisory relay to energize when the called subscriber answers and a supervisory signal controlled by said supervisory relay.

31. In a telephone system, a called line, trunking circuits and progressively movable switches for finding the called line to form a talking circuit, an operators supervisory relay bridged across the talking circuit, a pair of line relay coils, a battery adapted to be connected in series with said supervisory relay over acircuit including portions of the two sides'of the talking circuit, a high resistance relay in said circuit, an auxiliary automatic switch for short-circuiting said high resistance relay before the called line is found, to permit the operation of said line relaycoils, a magnet for operating said auxiliary switch for removing the short-circuit when the called line is found, to prevent said supervisory relay from energizing, and arelay controlled by the called subscriber for causing1 said supervisory relay to energize when t e called subscriber answers, together with a supervisory signal controlled by said supervisory relay.

32. In a telephone system, a progressively movable trunking line switch provided with a release magnet, a trunk adapted to .be seized by said line switch,-a relay for the end of the trunk adjacent the line switch, adapted to be energized over the two sides of the trunk, circuits for establishing a guarding potential for said trunk by the energizing of supervising such connection over the two said relay, and for energizin said rel ease- Inagnet by the denergizing 0:? said relay.

tential for said trunk by the energizing of said relay, and for energizing said release ma et by the deenergizing of said relay,

sai trunk provided with a condenser in eac side thereof, as and for the purpose set forth.

- 34.11: a; telephone system, a manual switch-board, a cord circuit associated with said board and automatic progressively movable switches operated successively in establishing'a talking circuit between a calling manual subscriber and a called automatic subscriber, a line and a line relay individual to each; switch, a relay'on saidboard for sides of the talking circuit, said relays en ergized over the two sides of one of said lines in series. 7 v

35. In a telephone system, a manual switch-board, a cord circuit associated with .said board and automatic progressively movable switches operated successively in gstablishing a talking circuit between a calling automatic subscriber and acalled manual subscriber, a relay individual to each of said switches, a relay on said board for supervising such connection over the two sides of the talking circuit said first relays energized over the two sides of said talking circuit in series to control said switches.

36. In a -telephone system, subscribers lines, trunk lines, suitable automatic switches for extending a .talking' circuit over said trunk lines from a calling to a called subscriber, a side switch and. a line relay for one, of said automatic switches operable over said talking circuit, means controlled by said line, relay for placing a guarding potential on a busy trunk, a magnet for operating said side switch to cut off said line relay from the talking circuit, and another relay energized over both sides of said talking circuit for maintaining-the connection busy when said v line relay is deenergizedy 37 Ina. telephone system, subscribers lines, trunk lines divided into groups, suitable automatic switches for extending a talking circuit over said trunk lines from a calling to a called subscriber, said switches hav- .ing vertical motion to select groups and rotary motion to find a line in a selected group, a sideswitch and a line relay for one of said automatic switches,means controlled by said line relay for placing a guarding potential on a busy trunk, a ma et for operating said side switch to out 0 said line relay from --rupted without destroying said the talking circuit another relay energized over both sides of said talking circuit for maintaining said busy connection when said connected'lme relay is deenergized. Y

38. In a telephone system, subscribe) lines, trunk-line, suitable automatic switches for extending a talking circuit over said trunk lines from a calling to a'called subscriber, a relay for one of said automatic switches adapted upon energization to place a guarding potential on a busy trunk, and

another relay energized over-both sides ofqsaid' talking circuit for holding said busy connection when said first rela", is deene'. gized. 4 Y

39. In a telephone system, subscribers lines, trunk lines divided into groups suit-.

able automatic switches for extending a talking circuitover said trunklines from a calling to a called subscriber, said switches havingvertical motion to select groups and rotary motion to find a line in a selected group, a relay for one of said automatic switches adapted upon ener ization to place a guarding potential on a usy trunk, and. means including a circuit comprising the two conductors of the talking circuit for maintaining said busy connection when said relay is deenergized. 1

40.- In a telephone system, subscribers lines, trunklines, suitable automatic switches for extending a talking circuit, over said trunk lines from a call1n'g to a called subscriber, a relay for placing a busy potential on a trunkline, said relay controlled over both sides of the talking circuit, and means whereby the talking circuit may be interrupted without destroying said busy condition.

41. In a telephone system, subscribers lines, trunk lines divided into groups suitable automatic switches for extendlng a talking circuit over said trunk lines from a calling to a called subscriber, said switches having vertical motion to select groups and rotary motlon to find a line in a selected group, a relay for placing a busy potential on a trunk, said relay controlled over both sides of the talking circuit, and means whereby the talking circuit mag be interusy condition.-

42. In a telephone system, subscribers lines, trunk lines, automatic progressively movable switches and a} cord circuit for establishin plurality 0% said trunk lines between two of said subscribers lines, a line and a line relay individual to' each. switch, said relays energized over the two sides of a portion of the talking circuit in series, and a relay for supervising said connection.

43. In a telephone system, subscribers line's, trunk lines, a manual switchboard,

suitable automatic switches operated succesa talking circuit including a 

